Lap grinding compound



Patented Mar. 19, 1940 UNITED STATES 2,193,965 PATENT OFFICE.

LAP GRINDING COMPOUND Carroll A. Hochwalt, Dayton, Ohio, assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware 3 No Drawing. Application June 3, 1939, Serial No. 277,185

12 Claims. (Cl. 51-280) n it is cleaned after the grinding operation.

The usual lap grinding compounds are composed primarily of an abrasive and the vehicle therefor together with minor'proportions of rust inhibitors, wetting agents, and the like. Some type of oil is usually employed as the vehicle, since a lubricating effect is desirable during the abrasive action, and also because it provides a relatively inexpensive and effective suspending medium for the abrasive. The usual oil vehicles,- however, require the use of detergents or relatively expensive methods of removal after the lap grinding operation has been completed. The difficulty of removal is not only troublesome but may be responsible for inferior products resulting 2 from the difficulty of making sure that the oil and abrasive mixture is completely removed.

The present invention provides a vehicle'which not only may be quickly and easily removed merely by washing with water but which, when. incor- 30 porated with an abrasive, forms a lap grinding compound which is much more efhcient than the same abrasive suspended in oil.

The suspending medium employed by the present invention is an aqueous solution of an alkyl 5 phosphoric acid salt. These salts may be presponding salt. The reaction, in the case of P205,

45 may be typified by the following formulas:

50 The neutralization reaction to form the corresponding sodium salts may be typified as follows:

. The R in each of the above six equations represents an alkyl radical. v 60 The neutralization shown above can, of course,

be efiected with substances other than sodium carbonate or sodium hydroxide. Part of the sodium carbonate can be substituted by a salt'like sodium. chloride, only enough sodium carbonate or sodium hydroxide being used to secure the de- 5 -sired alkalinity. Potassium or ammonium compounds may be used in the same manner for the production of monoor di-alkyl potassium or ammonium phosphates. Amines may also be em ployed and a particularly desirable product may be obtained by the use of triethanolamine or other hydroxy alkyl amines. For most purposes a final pH of from 6 to 8.5 will be found satisfactory.

Forthe purpose of this invention, it is not necessary separately to recover the reaction products 9 in the mixture of alkyl phosphates produced by the action of phosphorus pentoxide or a strong phosphoric acid with anhydrous aliphatic alcohols. The process of neutralization, however, is

7 made more simple if the trialkyl phosphate content of the mixture be kept at a minimum. When a mixture of varying proportions of mono and. di .alkyl' phosphates is neutralized with a basically reacting compound, a mixture of water-soluble,

Monosodium diethyl phosphate, 86 Monosodium diisopropyl phosphate,

I Monosodium di n-butyl phosphate,

Monosodiumdiisobutyl phosphate,

Disodium monoethyl phosphate,

Disodium monoisopropyl phosphate, Disodium monoisobutyl phosphate,

' Monosodium dlmethyl phosphate,

Diammonium monoethyl phosphate,

Triethylamine diethyl .phosphate,

Diethylamine diethyl phosphate,

Monoethylamine diethyl phosphate,

' Triethylamine diisopropyl phosphate, Triethylamine di n-butyl phosphate. 60

'Iriethylamine diisobutyl phosphate,

/ Tripropylamine diethyl phosphate,

Triisopropylamine diethyl phosphate, Dipropylamine diethyl phosphate. Monopropylamine diethyl phosphate. Triisobutylamlne diethyl phosphate,

m (triethyla'mine) monoethyl phosphate,

Di (diethylamine) monoethyl phosphate, Di (monoethylamine) .monoethyl phosphate, Trimethylamine diethyl phosphate, 00

Di (trimethylamine) monoethyl phosphate, Triethanolamine diethyl phosphate,

Di (triethanolamine) monoethyl phosphate, Triethanolamine diisopropyl phosphate,

Di (diethanolamine) monoisopropyl phosphate,

Monoethanolamine diisopropyl phosphate,

Triethanolamine di n-butyl phosphate, Triethanolamine diisobutyl phosphate, Tripropanolamine diethyl phosphate,

Di (tripropanolamine) monoethyl phosphate, Tripropanolamine diisopropyl phosphate, Tripropanolamine diisobutyl phosphate, Trimethanolamine diethyl phosphate,

Di (trimethanolamine) monoethyl phosphate, Dimethanolamine diisopropyl phosphate, Monomethanolamine diisobutyl phosphate,

.Triethanolamine dimethyl phosphate,

Monopotassium diethyl phosphate, Monopotassium diisobutyl phosphate, Dipotassium monoethyl phosphate, Potassium sodium ethyl phosphate, Monopotassium monoethyl hydrogen phosphate, Monosodium monoethyl hydrogen phosphate, Monopotassium monoisobutyl hydrogen phosphate.

The above list might be expanded almost indefinitely if every compound contemplated by the present invention were listed, but it has been limited to those only which are representative. In general, any salt of an alkyl phosphoric acid whose aqueous solutions have lubricating and humectant properties at room temperatures may be employed in carrying out the present invention. Mixtures of any of'the above materials may also be employed to prepare abrasive compounds contemplated by the present invention and, in fact, for mostpurposesit is usually preferable from a cost standpoint to employ mixtures.

Any of the customary abrasives used in lap grinding may be employed and they may be used in the usual proportions. However, as will be pointed out below, the use of the alkyl phosphate salts as suspending media in many cases will permit a decrease in the proportion of abrasive.

A typical formulation for a lap grinding compound, according to the present invention, is as follows:

1. 22.50% unfused aluminum oxide abrasive which grades 400 mesh,

2. 77.50% aqueous ethyl sodium phosphate solution (containing 70% by weight of water and by weight of solid alkyl phosphate made up of 65% diethyl and monoethyl sodium.phosphates).

To this material may be added, if desired, .1% to 25% sodium dichromate to act as an inhibitor of corrosion and .5% of any of the customary wetting agents. The resulting compound is very eifective for lap grinding operations and it will be found that it will cut approximately faster than the same compound when oil is substituted for the phosphate. Other proportions of abrasive may be employed, since, .for example, twice as much could easily be incorporated to form a compound having faster abrasive action. Because of this improved cutting action, a finer abrasive can be used to form a smoother finish or the proportion of abrasive can be reduced without incurring the penalty of a longer grinding time.

An outstanding advantage of the lap grinding compounds of the present invention is that they may be quickly and easily removed, merely by washing with water. The phosphate is highly useful for many purposes.

water-soluble and it, with the abrasive, is advantageously removed by a simple washing treatmerit. When oil is employed as the suspending medium, this is, ofcourse, not possible, and expensive detergents must be employed with attendant increase in the cost of the cleaning operation. Also, there is danger that all of the grinding compound will not be removed, which would interfere with subsequent operations, such as coating. This danger is important since the metal surface may appear bright and clean while still retaining sufilcient residual grease and fine metal particles to interfere with proper finishing. Although the phosphates are easily soluble in water, they have an oily viscosity which gives the desired lubricating effect when they are incorporated in lap grinding compounds.

Other alkyl phosphates may, of course, be employed, the outstanding example of which is methyl, although propyl and butyl phosphates are also a The alkali metal salts of weak acids and their hydroxides, as well as the corresponding basically reacting compounds of ammonia may be employed as the neutralizing agent, but important salts are also formed by the w use oi amines. Although the alkali salts of alkyl phosphoric acids are solid, they are strongly hygroscopic, so that, in general, no diiliculties are encountered in their use from drying out, but for especially dry conditions the amine salts are pref- 80 erable, since they are hygroscopic liquids and exhibit no tendency to crystallize. Such an amine alkyl phosphate containing compound may have the following composition:

85 l. 22.50% abrasive (unfused aluminum oxide),

2. 77.50% aqueous tricthanolamine ethyl phosphate solution (containing 70% by weight of water and 30% by weight of phosphate anhydrous base made up of diethyl and monoethyl triethanolamine phosphates).

The above composition is especially valuable where the relative humidity is quite low, as is frequently the case in cold weather.

The mixed alkali salts of alkyl phosphoric 4| acids may also be employed, the monoethyl sodium potassium phosphate giving very good results Also mixtures of the phosphates may be employed, as is outlined above, as well as mixtures of two or more diflerent types, for example, 20% or more of a mixture of equal parts of mono and diethyl sodium phosphates may be added to the triethanolamine phosphate salt described above in order to reduce the cost of the composition without decreasing its value for low humidin general preferable to neutralize the alkyl phosphate to a pH of about 7, this is not essential.

Since the lap grinding composition is removed merely by washing, the phosphate may, if desired, be recovered and reused. In general, how- (0 ever, the cost of recovery is not justified by the value of the recovered material.

Where the term alkali metal" appears in the claims it will be understood that the ammonium radical is included.

greases 2. A lap grinding compound. comprising an abrasive and an aqueous solution of an alkyl phosphate salt.

3. A lap grinding compound comprising an abrasive and a vehicle therefor comprising an aqueous solution of a'hygroscopic alkyl phos- 10 phate salt.

4. A lap grinding compound comprising an abrasive and sodium ethyl phosphate in aqueous solution. 7

5. A lap grinding compound comprising an 1 abrasive and triethanoiamine ethyl phosphate in aqueous solution.

6. The method of lap grinding which comprises using as the grinding compound an abrasive suspended in an aqueous solution of an alkyl phoso phate salt.

7-. A lap grinding compound comprising a'nabrasive and an alkali metal salt-o1 an aliwl phosphoric acid.

8. A lap grinding compound comprising an abrasive and an alkylamine salt of an alkyl phos:

phoric acid. a

9. A lap grinding compound comprising an abrasive and a trialkylamine salt of an alkyl Phosphoric acid; p v p v 10. 'A lap grinding compoundcomprising ah abrasive and an alkali metal salt of ethyl phosphoric acid.

-11. A lap grinding compound comprising an abrasive and an alkylamine salt of ethyl phosphoric acid.

12. A composition of matter comprisingan abrasive andan alkyl phosphate salt, said composition being characterized in that when employed as a lap grinding compound it may be substantially completely removed from the workpiece with water. I

CARROLL A. HOCHWALT. 

